A device whereby a desired pattern is marked onto a specimen by irradiating the specimen with laser light is disclosed in Japanese Patent Publication 4-39646.
In the device disclosed in this patent, reference marks are provided at prescribed intervals in the X direction at the specimen stage, photodetector elements are provided, laser light is scanned in the X direction prior to actual marking, the divergence .DELTA.X from the reference mark is determined for each reference mark from the timing at which light is received at each photodetector element, and the position of laser irradiation in the X direction is corrected for each reference mark on the basis of the divergence .DELTA.X for each reference mark.
However, in the aforementioned device, since the position is corrected in reference mark units, a memory having a very large memory capacity is required in order to record and store data on the divergence, .DELTA.X, for each reference mark, therefore leading to high costs. Furthermore, since it is necessary to read out and calculate computer data on the divergence, .DELTA.X, for each reference mark, time is required for processing and high-speed processing cannot be achieved.
On the other hand, in a laser marker already implemented by the present applicant, although the composition of the device, which is premised on the use of a liquid crystal mask, or the like, differs from the prior art laser marker described above, there is a demand for correction of the marking position to be carried out at low cost and high speed.
The present invention was devised in view of the foregoing, its object being to provide a laser marker wherein the marking position can be corrected by means of a simple calculational process using a small quantity of corrective data, thereby enabling reductions in cost and increases in speed to be achieved.